Control system for adding and removing alternators from a system

ABSTRACT

An automatic control system for a plurality of engine powered alternator units arranged to supply a common electrical distribution system wherein the alternators are driven by speed governed engines which employs circuitry which adds or removes units as the electrical load varies, calls all non-operating units when an overload is approached and removes any malfunctioning alternator unit due to mechanical and/or electrical malfunctions in the unit by employing voltage signals from commercial load profile modules for control functions and voltage signals from the engine governors.

United States Patent Wagner [4 1 Nov. 21, 1972' [54] CONTROL SYSTEM FORADDING AND 3,339,079 8/1967 Kessler ..307/86 X REMOVING ALTERNATORS FROMA 3,519,883 7/1970 Morey ..3l7/26 SYSTEM Primary Examiner-James D.Trammell [72] Inventor: Harold Wagner, Peoria, Ill. Attorney charlesFryer et aL [73] Assignee: Caterpillar Tractor Co., Peoria, 111. 57ABSTRACT [22] Filed: Sept. 10, 1971 i 1 l 1 f l l f n automatic controsystem or a p ura ity 0 engine [21] Appl' 179282 powered alternatorunits arranged to supply a common electrical distribution system whereinthe alterna- [52] US. Cl ..317/13 R, 307/86, 317/19, are driven by Speedgoverned engines which 317/26 317/27 ploys circuitry which adds orremoves units as the [51] lnt.Cl. ..l-l02h 7/06 elecirica' bad varies[58] Field 61 Search...307/85, 86, 84; 290/1; 322/69; when is aPlmmledand f 317/19 13 R 20 27 malfunctioning alternator unit due to mechanicaland/or electrical malfunctions in the unit by employ- [56] ReferencesCited ing voltage signals from commercial load profile modules forcontrol functions and voltage signals from UNITED STATES PATENTS. the gie g rnors- 3,300,648 l/ 1967 Rockefeller ..307/86 X 8 Claims, 4 DrawingFigures MAIN 1 7 i T 1 I23 I24 2 5 TY@* 1 r zssa SYSTEM 1 93556 .L F 115CM. 5?

116 iii l T VII/50.6? 15 1 1 BASE V4161 PATENTEDuuv 21 I922,

SHEET 3 [IF 3 LOAD PROFILE MODULE OUTPUT VS SYSTEM LOAD VOLTS I I I I II I I I I I ll Y Mam CNS L 1 4V LLB AOT CNS L l l I LAW AOT CNS I? l lI| 2Y L.B AOT CNS L A um CNS 0 R". m n w 1 5 a o .rZ mOmma I mu OnPROPORTIONAL GOVERNOR ACTUATOR CURRENT VS GOVERNOR SHAFT POSITION ADJUSTGOVERNOR RELAY TRIGGER POINT TO ACTUATOR CURRENT- FULL RACK GOVERNORSHAFT POSITION OR THROTTLE LOW IDLE INVENTOR HAROLD H. WAGNER AT TORNEYS CONTROL SYSTEM FOR ADDING AND REMOVING ALTERNATORS FROM A SYSTEMBACKGROUND THE INVENTION The present invention relates to a controlsystemthat is adapted to automatically add and remove engine poweredalternator units from common electrical distribution system supplyingelectrical power for various uses. In particular, the system is adaptedto add and remove engine powered alternator units of substantially thesame electrical output capacity each'of which is independently driven bya speed governed prime mover, such as internal combustion or gas turbineengine. Current day control systems for addingor removing engine poweredalternator units, in systems employing a number of such units,conventionally use relatively expensive meter relays to determine theload on the system and to sequence the order in which engine poweredalternator units are added .or removed from the distribution system.

When utilizingmeter relays to obtainzan indicationof the electricalpower supplied by individual engine powered alternatorunits, there is noindication of some of the malfunctions that may occur in the prime moversince the electrical power may not be effected. For example, it ispossible that the electrical power output of the engine poweredalternator unit may be its proportional share of the load while theprime mover is operating in an overloaded condition to maintain therequired electrical output, as a result of some mechanical enginemalfunction. Under these circumstances it is possible to seriouslydamage the engine without a control system which will automaticallyremove the unit which has a malfunctioning engine from the multiple unitsystem and replace itwith another unit.

In addition, currently available control systems make no provisions foreconomically calling all additional units when an overload conditionoccurs in the electrical distribution system. Thus, in prior art systemsan overload in the system often requires prolonged removal of some ofthe non-essential loads in order that non-operating units can. bestarted one .at a time to carry some of the additional electrical loadat which time a second unit will be started if the overload persists,until eventually enough units are added to :handle the overload.Thereafter, the non-essential load can be re-connected to the electricaldistribution system.

SUMMARY OF THE INVENTION The present invention solves these problems byutilizing inexpensive load profile modules that provide signalsindicating the actual electrical powerdemand-of the system, as well asthe electrical power being supplied by individual alternator unitsconnected in the distribution system and uses these voltage signals,

whose amplitude is proportional to true electrical cally malfunctioningunit is shut down and its electrical load shifted to another unit.

The control system also includes suitable protective circuits if theprime mover fails to start or ifthe alternator fails to synchronize withthe system load within preset time limits so the next unit in thesequence will be called and the unit being called is shut down. Also,the system includes suitable safety devices monitoring engine oilpressure, engine fuel flow and other operating parameters of the engineso that the alternator unit may be shut down, if mechanical problemsarise and its share of the load shifted to the next standby unit.

The control system may also include circuits for interchanging theoperating unit and the standby units in a sequence which permits anequal distribution of the total system operating time so that all unitswill have substantially the same total operating times, except for thosehaving malfunctions.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be moreeasily understood from the following detailed description of a preferredembodiment taken in conjunction with the attached drawings wherein:

FIG. 1 is a schematic circuit drawing, partially in I block form, of themaster control portion of the system; "FIG. 2 is a schematic circuitdrawing also partially in block diagram form, showing the unit controlportion of the system one of which is utilized for each individualengine powered alternator unit;

FIG. 3 is a plot of the voltage output versus percent of system loadsupplied as a signal from the commercially available load profilemodule; and

FIG. 4 is a plot of governor shaft position versus governor actuatorcurrent which is employed as a control parameter in the control system.

DESCRIPTION OF THE PREFERRED EMBODIMENT The control system for multipleengine powered alternator units of the present invention includes twobasic portions, one being the master control portion shown in FIG. Iwhich sequences the addition or removal of the individual alternatorunits in order to meet the electrical load demand on the electricaldistribution system and protect the system from electrical overloads.The other portion of the system includes a plurality of identicalcircuits, as shown in FIG. 2, which are the unit control circuitportions for each individual engine powered alternator unit. Theillustrated master control portion of the system is designed to acceptsignals from four alternator unit circuits, as illustrated in FIG. 2.Since these unit circuits are identical with one another, only one needbe described herein.

The master control circuit is divided into three major subcircuits;subcircuit 10 is the portion of this circuit for measuring the totalpower demand on the electrical distribution system and callingalternator units in sequence in accordance with power demand on theelectrical distribution system; subcircuit 11 is the circuit for callingthe additional engine powered alternator units in a predeterminedsequence; and, subcircuit 12 is a series circuit which is designed tocall all vnonoperating engine powered alternator units when a systemoverload occurs.

Subcircuit includes a system readout module 8 and a load profile module9 both of which are coupled to the electrical distribution system bus 7.This system readout module includes instruments for monitoring thevoltage, current flow, total power, power factor and other parameterscommonly monitored in electrical powered distribution systems. Asexplained above, the load profile modules measures the true powersupplied on the bus and converts it to aproportional voltage signal.Commercial, suitable load profile modules are manufactured by AmericanBosch Arma Corporation of Springfield, Massachusetts, andthe electricalsignal from the module is supplied on leads l4 and to the individualcall circuits in the system. The voltage level to the call circuit isadjusted by employing potentiometer 13 and potentiometers 16 connectedin parallel to adjust the voltage level for each individual call circuitwhereby they will trigger at different voltage levels. The individualcall circuit comprises an operational amplifier 17 whose output isconnected to a voltage sensitive relay which is activated when the callcircuit triggers. A Schmitt trigger circuit and relay may be used inplace of the operation amplifier and voltage sensitive relay. Each ofthe call circuits shown have a voltage sensitive relay 18, I9 and 20,respectively, and which for convenience are also labeled CA-l, CA-2 andCA-3 on-the drawings, and when the voltage level to the operationalamplifier input exceeds a certain level, the amplifier will trigger andactuate its associated voltage sensitive relay.

Voltage sensitive relays 18, l9 and can be of the delay type so that thetriggering voltage level will be required to remain above the triggeringlevels for periods of five or so secondsbefore the relay will close tocall a standby engine powered alternator into operation. Similarly,these relays should include delay circuits to prevent shut down untilthe trigger signal remains below the triggering level for apredetermined period; i.e. for 5 to 15 minutes. Utilizing time delaytype relays prevents minor temporary fluctuation in electrical load fromcycling the several cal] relays. Each of the voltage sensitive relaysincludes two sets of contacts, one set being closed at the time theother set is open. For example, voltage sensitive relay 18 includesnormally closed contacts 18a and normally open contacts 18b which aredisposed in the controls of subcircuit 11 for calling the individualunits in a predetermined sequence. Similarly, relay 19 includes contacts19a and 19b and relay 20 includes contacts 20a and 20b which functionidentically. Upon actuation of these relays the open contacts will closeand the closed contacts will open.

The series call circuit 12 of the master unit is composed of parallelrelay. contacts 34b and 78a which are actually part of each individualunit control circuit portions that are connected in the same order orsequence that their associated unit is connected into the master system.Thus, each set of relay contacts provide a portion of a series connectedcircuit between the positive battery source and a lead 23 through adiode 24 which connects through a resistance to lead 15 from the.profile module. As a result, if at least one contact isclosed in each ofthe parallel pair of contacts a positive voltage will be supplied tolead 15 which is in excess of the voltage to actuate all of the triggercircuits in the call circuits. Thus, this will cause all of the relaysl8, l9 and 20 to activate at once. This provides for a system by whichall the nonoperating units are called should an overload occur in theelectrical distribution system. The relay contacts are designated as 34band 78a and each parallel set also includes designations of GR and .TRto'indicate that they are operated by particular relays in theindividual unit control circuits described in greater detail below. j y

Assuming the system is shut down, the initial start-up procedure will bedescribed with the unit control circuit illustrated in FIG. 2 pluggedinto the base plug of the master circuit shown in FIG. 1 and additionalunit control circuits are plugged into the number 1, 2 and 3 plugs.Initially, S-l switch 28 (FIG/1) is closed to supply the voltage ofbattery 29 to the DC battery busses 30 and 31. This will cause each unitcontrol circuit to have DC power on its extension of the battery bus 30.Before the DC busses are electrified, the 8-2 switch of the base unitconnected to the base plug is turned to its automatic position while allthe other S-2 switches of unit control circuits 1, 2 and 3 are placed inthe manual position for start-up. Thereafter units 1, 2 and 3 can beswitched to their automatic mode after the base unit hasbeen connectedto the electrical distribution system, bus 7.

' Referring to FIG. 2, the 8-2 switch is shown in the automatic positionand the initial start-up will now be discussed. With 8-2 switch in autoposition in the base unit, positive DC power will be supplied to theunits secondary positive bus 30a that will supply positive power torelays 33, 34, 35, 36, 37, 38, and 39. As a result, when the switches inthe relay circuits are closed connecting them to ground, these relayswill actuate and operate their control contacts. Initially, the switchesformed by the contacts of the several relays will be in a position asindicated in FIG. 2 and CR cranking relay 39 will commence cranking theengine and the CRT cranking relay timer 38 will commence timing thecranking cycle of the engine. During this cycle, if the engine fails tostart, the timer after 30 seconds will close contacts 38a to relay 41which will activate to open contacts 41a and close contacts 41b. Thisrelay is a latching type so it will remain with contacts 41b closeduntil reset. Closing contacts 4lb will connect the SR shut down relay 42to the DC bus and its activation will open contacts 42a and closecontacts 42b and 42c. Opening contacts 42a will disconnect the positivepower from the secondary bus 30a and thus to all relays 33, 34, 35, 36,37, 38 and 39. as well as deactivate the fuel solenoid 32 shutting downthe engine. Further closing of contacts 420 will put positive DC busvoltage on lead P-1 which will drop-the unit from the sequence operatingthe SQ sequencing relay (FIG.

.If the engine starts within 30 seconds, an oil pressure switch 50 willconnect .relay 37 to ground through switch 50b which will actuate thisrelay and open con-- tacts 37a and 37b, and close contacts 37c and 37e.As a result, the cranking relay timer will be deactivated prior to its30 secondrun out and the cranking relay 39 will disengage stopping thecranking of the engine while the synchronizing timing relay 36 will beactivated and commence timing the end of the preselected interval forreaching electrical synchronization with loads on the primarydistribution bus '7. Contacts 37d will alsobe closed by actuation ofrelay 37 but since the pressure .switch opens contacts 50a as it closesswitch 50b relay '40 will not actuate to shut down the system aspreviouslydescribed by clos ing contacts 40b and opening contacts 40aand 40b which would actuate the-shutdown relay 42. lfoi'l pressure islost, however, contacts 50a will'close activating this relay and theshut down relay 42. Contacts 3% latch relay 37 on when oil pressure islost preventinga start recycle.

When the base unit starts it will be directly connected to the power bus7 to supply the load as soon as its voltage builds up. If the generator.field 51 is under excited the base unit voltage does notbuild up toanappropriate value and the 'field relay 152 will not operate. Contacts52a thus will not close to operate load relay 35, hence relays 33 and 34cannot operate and the-circuit breaker controls will not function "toconnect the unit to the system bus. The synchronizing timer 36 thereforeremains energized to time out after :sixty seconds and actuate to closeits contacts 36a to energize the PST power shut down relay timer 43.After '3 minutes this relay will actuate tOfClOSC contacts 43a toenergize the power shut down relay 44 which will operate to opencontacts 44a and close contacts 44b which will power the shut down relay42, previously described, which will shut downthe engine.

Relays similar to 40, 41 and 42 can be employed with similar associatedcircuitry to handle temperature-overloads or other malfunctions in theunits enginecircuitry to protect the unit from damage and need not bedescribed. I

When the base unit is started, there is no power on bus 7 and thereforecircuit breaker .103 can be closed immediately'powering the bus throughthe three phase alternator of the base unit when its voltage is built upand the circuit breaker is armed forclosing. When field 51 is properlyexcited relay 52 will operate closing its contacts 52a to actuate loadrelay '35 through spring contacts 111 which are closed when the circuitbreaker is armed. This will close contacts 35a and 350. Since there isno power in the .main bus the dead bus relay 102 will have its'contacts1'02band 102cclosed with its contacts 102a open which will allowsynchronizing relay 104 to operate, closing its contacts 104a and 104b,when contacts 350 close. As contacts 104a close relays 33 and 34 areactuated to cause contacts 33a 33c, 33d, 34c and 34d to close whilecontacts 33b, 34a and 34b will be opened. Relays 33 and 34 are latchedin the actuated position bythe closing of contacts 33a and the openingof contacts 34a will cutoff the synchronizing timing relay 36 preventingactivation of the shut down relay 42 at the end of the predeterminedtimed cycle.

As the primary bus becomes powered, the dead bus relay 102 will beactivated and its contacts 102a and 1020 will be closed and its contactsl02b will be opened. Further, this activation will take place in all theother unit controlcircuits since the primary bus will be powered andactivate their dead :bus relays. With contacts 102b opened, transformers100 and 101 will be powered one from the alternator coming on the lineand one from the bus 7 by connection B. The connection B is energizedfrom one phase of the system bus by a transformer 130. When this occursin the base unit,

the relay 35 has already closed its contacts 35c perrelay 1'05 and avoidshutdown'at the end of the period measuredby'the synchronous timer. Oncesynchronization is obtained, the circuit breaker power unit will closecircuit breaker 103 adding the alternator unit to the distribution bus7. The motor armature 106 is used for arming or tensioning the springused for powering thecircuit breaker. When an oncoming unit is startedthecircuit breaker spring, not shown, is armed for closing by a circuitconsisting of breaker auxiliary contacts 103b, travel limit contacts108, field winding 112 and armature 106 across a single phase of thealternator output. Whenthe spring is armed spring contacts and 111 willbe closed and travel limit contacts 107 and 108 will be opened therebystopping rotation of armature 106. When the oncoming unit is up tovoltage and synchronized relays 33, 34 and 35 are actuated as previouslydescribed causing contacts 33 c and 340 to close and contacts 35b toopen. When contacts 340 close an actuating circuit is completed forcircuit breaker power unit 105 through the closed spring conreclose.Opening spring contacts 111 causes load relay 35 to temporarily restorepermitting contacts 35b to reclose. 'This action again powers armature106 through field winding 114, contacts 107, 33c and 35b to arm thecircuit breaker spring in a direction to cause the circuit breakertoopen when called forby the controls. When the spring is armed foropening, contacts 107 and 108 will again be opened and spring contacts.110 and 111 are again closed. A shunt trip relay 27 in the unitcontrols is conditioned by the closing of breaker auxiliary contacts1030 when the circuit breaker is closed and this relay will operatesimultaneously with relay 42 in any subsequent shut down operation.Shunt trip relay operation closes contacts 27a completing a circuit tocircuit breaker power unit 105 which releases the armed circuit breakerspring to open circuit breaker 103. The circuit breaker and its drivesystem are commercially available units.

Assuming the particular unit is not shut down for any one of the reasonsdiscussed above,-as it is connected to the bus, the unit readout system"59 will provide information to the profile module 60 whose output willbe proportional on lead 61 and 62 to the true power being generated bythe alternator. Leads 61 and 62 are connected across the potentiometer63 and its output 64 is employed in the governor computer control 71.The governor computer 71 is of a commercial integrated circuit type suchas that built by American Bosch Arma Corporation, and known as type 564whose output can be sent over leads 72 and 73 to the governor actuatorlated to total engine output and a signal taken across a voltage dividernetwork 76 is sent to an operational amplifier 77 for a controlparameter. Since the governor setting for full engine output is known,if the signal to operational amplifier 77 becomes greater than fullpower, the operational amplifier will trigger and operate governor relay78 which will close contact 78a in the series circuit 12 (FIG. 1) forits unit and also close contacts 78b which will activate the malfunctiontimer relay 79. This malfunction relay is a timing relay and afterseconds, if it is still activated it will close contact 79a activatinglatching malfunction relay 80 which then will close contacts 80b andopen 80a. This will energize the power shutdown relay 43 andsimultaneously put positive battery on lead 45 which is communicated vialead P-l to sequence relay 115 (FIG. 1) to start the next unit. Afterthree minutes relay 43 will actuate and close contacts 43a causing thepower shutdown relay 44 which is the latching type to close contacts 44band open contacts 44a, thereby powering shutdown relay 42 which willshut down the unit as previously described.

The individual unit control system also includes a .reverse currentprotector circuit similar to the protective circuit for impropergovernor and power output relationships. The reverse current protectioncircuit prevents an alternator from operating like a motor when it failsto deliver the appropriate amount of power while it is connected to thepower bus 7. This will occur only when the system is being supplied bytwo or more alternator units and when one fails to deliver any power.Under such circumstances, it is driven as a sychronous motor by otheralternator units with the higher power output. If such reverse currentflow occurs, the output of the profile module will change polarity whichwill be reflected in leads 85 and 84 which connect to an operationalamplifier 86. This amplifier will trigger if the output of the profilemodule assumes the negative value and will actuate reverse current relay87. Actuation of reverse current relay 87 will close contacts 87a whichwill cause the special purpose latching relay 88 to close its contacts88b and open its contacts 88a thereby actuating the shutdown relay 42whose operation has been previously described.

After the base unit has been coupled to the system, it

will supply power until the load on bus 7 increases to a Operationalamplifiers 77 and 86 are relatively low cost units, such as thatmanufactured by Sensitac lnstrument Corporation in Manchester, NewHampshire, which include the adjustable operational amplifiers thatpermit triggering at any input level of either a positive or negativevalue. Through the utilization of the above circuits, it is possible tosubstitute these relatively low cost units for the conventional reversecurrent power relay and measuring devices used to detect suchmalfunctions in conventional control system of this type. Further, thearrangement detects a malfunction determining if a particular unit issupplying its proportional share of the load as related to an enginegovernor position. This is a more accurate indication of the properfunctioning of the unit than measurements such as fuel flow or actualpower being supplied by the alternator, used separately.

point approaching that of the capacity of the base engine power andalternator unit. This situation will be indicated by the voltage fromthe system profile module increasing as the true power output of theunit increases. When the voltage point set by potentiometer 16 isreached call relay 18 will be actuated due to the triggering of the callcircuit 17 associated. Actuation of this call relay will cause contact18b to close and contacts 18a to open. As a result of the changing ofthese contacts, lead P2 of the engine powered alternator unit connectedto position 1 (shown in FIG. 1) will be powered through its switch S2.Of course, after the base unit has been connected to the bus 7, theswitches S2 in the remaining units are shifted to the automatic positionso the above sequence will automatically occur.

Referring to both FIGS. 1 and 2, it can be seen that as switch S2 ifplaced in either the manual or the off position will supply positivepower through lead P1 to sequencing relay (SQ1) which will cause itsplurality of contacts controlled by actuator 11511 to shift the contactsin call circuits 11. As a result of this contact shift, the unitconnected to position 1 is removed from the sequencing operation.Further, it should be appreciated, that should a malfunction occurwhereby the synchronous timer relay 36 of one of the units actuates itscontacts 36a a positive power will be supplied through lead 45 backthrough the lead P1 to sequence the sequence relay associated with thatparticular unit. Thus, in the instant case, should the base unitmalfunction sequence relay 115 will shift to remove this unit fromfurther operation in the circuit. Similarly, if the unit connected tothe 1 position of FIG. 1 has a malfunction or is switched to manual, itwill operate sequencing relay 116 whose actuator 116a will repositionits contacts to remove this unit from further operation. Similarly, theunit connected to position 2 would likewise power lead P1 which wouldoperate sequencing relay 117 whose actuator 117a would remove this unitfrom the circuit. With all the units operating normally, the sequencingrelays described above would be in a position shown in FIG. 1.

Referring to FIG. 3, a voltage versus power trace is shown for thesystem profile module with the voltage line having spaced indicationsthereon where, through adjustments of potentiometers 16 of the variouscall circuits 17, the alternator units will be actuated. Thus, as thetrue power, converted to volts, increases due to increased power demandson the system, the individual units will be called in order and added tothe distribution bus 7 to avoid an overloaded condition. In theparticular voltage curve shown, the individual call circuits oramplifiers l7 operate on increments or steps of 3 volts.

This system employing a voltage signal proportional to true power is animprovement over prior art systems that use complicated mechanicalarrangements in order to call the standby units as the load increases.Since the voltage curve is available which represents the true powerdemand on the circuit it can also be employed to remove units from thesystem and as the voltage of the system profile module drops towardzero, units will be removed from the system until only the base unitremains.

It is to be appreciated that these units which are operating have bothparallel contacts 34b and 78a in the open position since actuation ofrelay 34 when the alternator comes on the line will open contacts 34b.However, the units which are not operating will have at least one oftheir parallel contacts, in this case 34b, closed which'will completethe series circuit except for the operating unit or units which havetheir pairs of contacts open. lf an overload occurs, the operationalamplifier 77 will trigger the governor relays 78 of all operating unitsand this will cause the contacts 78a of the operating units to closethereby completing the series circuit. As this occurs, the positivevoltage will be applied to lead and all call circuits willbesim'ultaneously actuated since the voltage is set above the 15 voltsrequired to activate all call circuits 17. As a result, call relays 18,19 and 20. may be actuated to start. and bring all nonoperating units upto speed and eventually parallel them with the power distribution bus 7when they reach synchronization. Of course, since the initial closure ofthe governor relay only activates a three minute malfunction timer, itis possible for the system to continue to operate before a shutdown ofthe operating units experiencing the overload occurs. Further,'if theoverload condition is'correct'ed prior to the timing of the malfunctiontimer relay 79 the overload condi-. tion may correct itself and none ofthe operating units will shut down. v

The voltage that triggers the series call circuit 12 also operates theoverload timing relay 120. The overload timer relay can be set for anydesired time delay, for example cight seconds, after which it willoperate the overload relay 12] by closing contacts 120a. When theoverload relay is actuated, it closes contacts 121a which causes thenon-essential trip 122 to trip its breaker 123 which disconnects thenon-essential load bus 124 from bus 7. The overload relays will alsoclose contacts l2lb connecting the battery bus voltage to relay 120through the terminals D in FIGS. 1 .and2. This maintains the overloadtimer in the on position until reset as long as any unit bus isconnected to the distribution bus 7 and prevents reclosure of thenon-essential load trip 122 until all unitsare running and cou pled tothe bus 7. If the overload timer was not powered from the battery, itwould be possible for the series circuit 12 to be broken when thenon-essential load was removed and the governor of any operatingunitcaused its associated relay 78 to be d'eenergized. This would remove thebattery voltage'from-the call circuits and non-operating units would notbe started.

Once all the non-operating units are started and synchronized with thecommon load bus 7, the positive power will be removed from the callcircuits since the series circuit12 will be broken by the opening of all34b contacts. The overload relay timer 120 will then be de-energized andthe non-essential load breaker will reclose. The system will then beoperating normally and the call circuits will then be controlledaccording to the power demand on the system. If the load is decreased toa point where all units are not needed, then all the units will continueto run until the call circuits are reset, for example, 15 minutes. Thecall circuit will then start shutting down units in the predeterminedsequence until the proper balance of the operating units and system loadis reached.

From the above description it is seen that in the case of an overloadall units are called simultaneously and synchronized with the loadbefore the non-essential load is restored. When the non-essential loadis restored, the number of operating units are balanced with the systemload demand by the call circuits.

OPERATION not shut down by the operation of a cranking timer or I theother safety devices. When the unit is up to operating voltage thesynchronizing circuit will operate to close the circuit breaker andcouple the operating base unit to the system load bus 7. As explained,the dead bus relays DB of all units will not be energized when no unitis supplying the system and the two synchronizing transformers 101 andwill be supplied directly from the operating unit. This insures that theinitially started or base unit will be coupled to the system load whenits voltage builds up. When the base unit has been coupled to the systemload, it will energize the dead bus relay to couple the transformers 101of all units to the system neutral. Thus, additional units mustsynchronize with the system load bus before they are coupled to thesystem load. The base unit will energize the relays 33 and 34 toreposition all their associated contacts and break the series circuit12.

Afterthe operating unit has been on the line for at least the resetcycle of the call circuits, for example, 15

minutes, the remaining switches S of the non-operating units can be setto the automatic position and additional units will not start unless thesystem is overloaded. If the call circuits are not reset prior toswitching standby unit controls to automatic, the nonoperating unitswouldimm'ediately go through their starting cycles and synchronizingthemselves with the system load. This, of course, results from the factthat the call circuits contacts would be closed and apply positive powerto the starting circuits of all non-operating units.

As the load of the system increases, the system load profile module 9will monitor the increase and supply a voltage signal to the callcircuits. When the voltage reaches the operating level of the first callcircuit relay 18 will energize and close the contacts 18a and opencontacts 18b. This will supply positive power to the first standby unitwhich will then start as set forth above. When the standby unit is up tooperating speed, it will synchronize with the system load since the deadbus relay will be energized and the DB contacts 1020 will be closedwhile the contacts 102b will be opened. This will insure that thetransformer 100 is energized from one phase of the standby unit whilethe transformer 101 is energized from the synchronizing bus. When thetwo transformers are synchronized, the synchronizing relay 104 willclose and close the contacts 104a. This in turn will cause the circuitbreaker 103 of the standby unit to close and couple it to the system bus7.

The above sequence will be continued as long as the system loadgradually increases or decreases. Of course, if a sudden overload shouldoccur the overload relay 121 will be energized as a result of the seriescircuit 12 being completed by the closure of all'eontacts 78a of theoperating units. This will immediately apply positive voltage to allcall circuits of a sufficient magnitude to call all non-operating units.The non-operating units will then start and synchronize with the systemas explained above. When all units have been started and synchronizedwith the system load, the overload relaywill be ie-energized and thenon-essential load restored. After resetting the call circuits, theywill take over their normal function and shut down the operating unitsuntil the number of operating units corresponds with the magnitude ofthe system load.

in the case of any malfunction in any operating unit, its associatedmalfunction timer 79 will be energized which in turn will energize theshutdown relay 42 to shut the unit down by opening contacts 42a andshift its share of the load to the next non-operating standby unit. Thiswill beaceomplished by applying positive power to the terminals P1 inFIG. 2 which in turn will operate the appropriate sequence relay inFIG. 1. While the malfunction may be a typical one, such as low oilpressure, high temperatures and the like, it can also be the case wheremeasured parameters are normal but the unit is not supplying itsproportional share of the load. In this case, the voltage sensitiveamplifier 77 will be energized by the increased current supplied to thegovernor positioning coil 74. This will energize the'governor relay 78which will close the contact 78b to start the malfunction timer 79. ifthe malfunctioning engine does not cure itself within the timers normaloperation of 20 seconds, the shutdown relay 42 will be energized whichin turn shut down the unit and shift its load to the next standby unit.

If any base unit is called and fails to start, the crank timer 38 willtime out in 30 seconds andthe oil pressure switch 50 will not close.When the crank timer times out, it closes contacts 38a to energize relay4]. This .will open the contact 41a and close the contact 41b to applythe positive power to the shutdown relay 42. This in turn opens thecontact 42a to'shut off the fuel to the engine and interrupt the powerto the crank solenoids, and close the contact 42b to apply positivepower to the line Pl which is coupled to the sequencing relay of thenext non-operating or standby unit No. 1. For example, if the base unitfailed to operate the line P1 would be coupled to the sequence relay 115in FIG. 1. This would energize the sequence relay 115 which would closethe contacts 115a and apply positive battery to the line P2 of the nextunit. This would start the standby unit which in turn would placepositive battery on the next on light of the next sequenced unit.

While the invention has been described with relation to internalcombustion engine prime movers, it can be applied to any type of primemover that can be automatically started. Also while specific sensitiverelays and load profile modules have been given, others may be used ifthey are capable of operating in a similar manner.

lclaim:

l. A control system for a plurality of separately engine drivenalternator units supplying a common elecll. trical distribution systemwherein at least one of said units acts as a base unit initiallyenergizing said electrical distribution system comprising:

a master circuit;

a plurality of identical unit circuits coupled to said master circuit,one of said unit circuits associated with each of said engine drivenalternator units;

electrical load sensing means connected to said distribution system tomeasure electrical power being supplied by said system and coupled tosaid master circuit;

call circuit means connected to receive an output from said load sensingmeans, said call means being connected through in said master circuit toeach unit circuit and operable to progressively activate and deactivatesaid unit circuits in relation to electrical load measured by said loadsensing means;

unit starting means in each unit circuit coupled to its controls for itsassociated engine driven alternator unit operable to start itsassociated engine when its unit circuit is activated by said callcircuit means;

unit shut-down means in each unit circuit coupled to its controls forits associated engine driven unit operable to shut down its associatedengine when its unit control circuits are deactivated;

malfunction circuit means in each unit circuit connected to separatelyactivate said shut-down means with its unit circuit activated, saidmalfunction circuit means including a unit load profile module connectedto measure the electrical power output of its associated alternator andgovernor amplifier with a comparator connected to receive the outputs ofsaid load profile module and said governor amplifier whereby disparitybetween the operation of its engine and its alternator output willproduce a malfunction signal, and

sequencing means in said master circuit connected to each malfunctioncircuit means operable to remove any unit from operation when amalfunction occurs in its malfunction circuit means.

2. The control system defined in claim 1 wherein the master circuitincludes a circuit capable of activating all the standby enginealternator units when the electrical load exceeds a predetermined level.

3. The control system defined in claim 1 wherein the load distributionsystem includes a main bus and a nonessential bus and the master circuitincludes a normally closed relay circuit connecting said non-essentialbus to said main bus and a load circuit opening said relay circuit whenthe electrical load exceeds a predetermined level.

4. The control system of claim 1 wherein said call circuit meanscomprises a plurality of parallel circuits including amplitude sensitivemeans responsive to the amplitude of the load as measured by a loadsensing means in said master circuit; said parallel circuits beingadjusted to operate in sequence as said load varies.

5. A control system for shutting down one of a plurality of enginedriven alternator units in response to a malfunction in said one unitcomprising:

a load measuring means, said load measuring being disposed to measurethe true power being supplied by the alternator of each unit and supplya signal related thereto;

a governor, said load measuring means being coupled to said governor toposition said governor and said governor being disposed to control saidengine; and

a malfunction detecting means being coupled to said governor to measurethe setting of said governor and compare it with said signalrepresenting the true power of its alternator, said malfunctiondetecting means being disposed to operate whenever the comparison givesan improper relationship to shut down said unit.

6. The control system of claim wherein the engine driven alternatorunits supply a common load, said control system including means forgenerating a signal representing the portion of the common load to becarried by each unit coupled to the load, said governor including meansfor comparing the portion of the load to be carried by a unit with thetrue power being supplied by each unit, said governor controlling itsengine so that its unit supplies its portion of the load.

7. The control system of claim 6 wherein said governor includes agovernor control coupled to the load measuring means and disposed tosupply an electrical signal to the governor to set said governor, saidmalfunction detecting means comprising circuit means responsive to theamplitude of said electrical signal to operate when said amplitudeexceeds a preset maximum.

8. The control system of claim 7 wherein said malfunction detectingmeans also includes means to call all non-operating units when said loadmeasuring means senses a system overload.

. UNl'llfil) S'IA'IES IA'II'IN'I m vuzw CERTIFICATE OF CORRECTION 2Patent; N ,7 Dated November 21 197 Inventor(s) Harold W gner It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In Fig. 2,, the intersection of the wires close to relay contacts 42aand adjacent to the fuse connected therewith should include a dot sothat these wires are conductively connected, therby connecting bothsolenoid coil 32 and lead 30a to the fuse. 7 Also the extra leadconnecting the fuel solenoid coil 32 directly to ground should bedeleted.

Below is illustrated the central portion of Fig. 2 with these changesincorporated therein.

ILL

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents ORM PO-1050 (10-69) usco'MM-Dc eo316-|= e9 9 U.S. GOVERNMENTPRINTING OFFICE: IQD 0-365-334,

UNl'llll) S'IA'l'ES IA'IICN'! owner: CERTIFICATE OF CORRECTION 3,703,663November 21, 1972 Patent No. Dated I Inventor-(s) Harold H. Wagner It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In Fig. 2, the intersection of the wires close to relay contacts 42a andadjacent to the fuse connected therewith should include a dot so thatthese wires are conductively connected, ther by, connecting bothsolenoid coil 32 and lead 30a to the fuse A the extra lead connectingthe fuel solenoid coil 32 directly to ground should be deleted.

Eelow is illustrated the central portion of Fig. 2 with these changesincorporated therein.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents -ORM PO-105O (10-69) uscoMM-Dc 60376-1 69 9 11,5. GOVERNMENTPRINTING OFFICE: 1969 0-366-334.

1. A control system for a plurality of separately engine drivenalternator units supplying a common electrical distribution systemwherein at least one of said units acts as a base unit initiallyenergizing said electrical distribution system comprising: a mastercircuit; a plurality of identical unit circuits coupled to said mastercircuit, one of said unit circuits associated with each of said enginedriven alternator units; electrical load sensing means connected to saiddistribution system to measure electrical power being supplied by saidsystem and coupled to said master circuit; call circuit means connectedto receive an output from said load sensing means, said call means beingconnected through in said master circuit to eaCh unit circuit andoperable to progressively activate and deactivate said unit circuits inrelation to electrical load measured by said load sensing means; unitstarting means in each unit circuit coupled to its controls for itsassociated engine driven alternator unit operable to start itsassociated engine when its unit circuit is activated by said callcircuit means; unit shut-down means in each unit circuit coupled to itscontrols for its associated engine driven unit operable to shut down itsassociated engine when its unit control circuits are deactivated;malfunction circuit means in each unit circuit connected to separatelyactivate said shut-down means with its unit circuit activated, saidmalfunction circuit means including a unit load profile module connectedto measure the electrical power output of its associated alternator andgovernor amplifier with a comparator connected to receive the outputs ofsaid load profile module and said governor amplifier whereby disparitybetween the operation of its engine and its alternator output willproduce a malfunction signal, and sequencing means in said mastercircuit connected to each malfunction circuit means operable to removeany unit from operation when a malfunction occurs in its malfunctioncircuit means.
 1. A control system for a plurality of separately enginedriven alternator units supplying a common electrical distributionsystem wherein at least one of said units acts as a base unit initiallyenergizing said electrical distribution system comprising: a mastercircuit; a plurality of identical unit circuits coupled to said mastercircuit, one of said unit circuits associated with each of said enginedriven alternator units; electrical load sensing means connected to saiddistribution system to measure electrical power being supplied by saidsystem and coupled to said master circuit; call circuit means connectedto receive an output from said load sensing means, said call means beingconnected through in said master circuit to eaCh unit circuit andoperable to progressively activate and deactivate said unit circuits inrelation to electrical load measured by said load sensing means; unitstarting means in each unit circuit coupled to its controls for itsassociated engine driven alternator unit operable to start itsassociated engine when its unit circuit is activated by said callcircuit means; unit shut-down means in each unit circuit coupled to itscontrols for its associated engine driven unit operable to shut down itsassociated engine when its unit control circuits are deactivated;malfunction circuit means in each unit circuit connected to separatelyactivate said shut-down means with its unit circuit activated, saidmalfunction circuit means including a unit load profile module connectedto measure the electrical power output of its associated alternator andgovernor amplifier with a comparator connected to receive the outputs ofsaid load profile module and said governor amplifier whereby disparitybetween the operation of its engine and its alternator output willproduce a malfunction signal, and sequencing means in said mastercircuit connected to each malfunction circuit means operable to removeany unit from operation when a malfunction occurs in its malfunctioncircuit means.
 2. The control system defined in claim 1 wherein themaster circuit includes a circuit capable of activating all the standbyengine alternator units when the electrical load exceeds a predeterminedlevel.
 3. The control system defined in claim 1 wherein the loaddistribution system includes a main bus and a non-essential bus and themaster circuit includes a normally closed relay circuit connecting saidnon-essential bus to said main bus and a load circuit opening said relaycircuit when the electrical load exceeds a predetermined level.
 4. Thecontrol system of claim 1 wherein said call circuit means comprises aplurality of parallel circuits including amplitude sensitive meansresponsive to the amplitude of the load as measured by a load sensingmeans in said master circuit; said parallel circuits being adjusted tooperate in sequence as said load varies.
 5. A control system forshutting down one of a plurality of engine driven alternator units inresponse to a malfunction in said one unit comprising: a load measuringmeans, said load measuring being disposed to measure the true powerbeing supplied by the alternator of each unit and supply a signalrelated thereto; a governor, said load measuring means being coupled tosaid governor to position said governor and said governor being disposedto control said engine; and a malfunction detecting means being coupledto said governor to measure the setting of said governor and compare itwith said signal representing the true power of its alternator, saidmalfunction detecting means being disposed to operate whenever thecomparison gives an improper relationship to shut down said unit.
 6. Thecontrol system of claim 5 wherein the engine driven alternator unitssupply a common load, said control system including means for generatinga signal representing the portion of the common load to be carried byeach unit coupled to the load, said governor including means forcomparing the portion of the load to be carried by a unit with the truepower being supplied by each unit, said governor controlling its engineso that its unit supplies its portion of the load.
 7. The control systemof claim 6 wherein said governor includes a governor control coupled tothe load measuring means and disposed to supply an electrical signal tothe governor to set said governor, said malfunction detecting meanscomprising circuit means responsive to the amplitude of said electricalsignal to operate when said amplitude exceeds a preset maximum.